{"cve":"CVE-2026-64114","nvd":{"published":"2026-07-19T16:17:52.820","modified":"2026-10-19T21:17:24.063","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: raw: reject IP_HDRINCL packets with ihl < 5\n\nraw_send_hdrinc() validates that the caller-supplied IPv4 header\nfits within the message length:\n\n    iphlen = iph->ihl * 4;\n    err = -EINVAL;\n    if (iphlen > length)\n        goto error_free;\n\n    if (iphlen >= sizeof(*iph)) {\n        /* fix up saddr, tot_len, id, csum, transport_header */\n    }\n\nIt does not, however, reject ihl < 5.  For such a packet the\n\"if (iphlen >= sizeof(*iph))\" branch is skipped, leaving the\ncrafted iphdr untouched, but the packet is still handed to\n__ip_local_out() and onward.  Downstream consumers that read\niph->ihl assume a sane value: net/ipv4/ah4.c:ah_output() in\nparticular subtracts sizeof(struct iphdr) from top_iph->ihl * 4\nand passes the (signed-int-negative, then cast to size_t)\nresult to memcpy(), producing an OOB access of length close to\nSIZE_MAX and a host kernel panic.\n\nAn IPv4 header with ihl < 5 is malformed by definition (RFC 791:\n\"Internet Header Length is the length of the internet header in\n32 bit words ... Note that the minimum value for a correct header\nis 5.\").  The kernel should not be willing to inject such a\npacket into its own output path.\n\nReject \"iphlen < sizeof(*iph)\" alongside the existing\n\"iphlen > length\" check.  This matches the principle that locally\nconstructed packets that re-enter the IP stack must pass the same\nbasic sanity tests that a foreign packet would be subjected to.\n\nOnce this lands, the \"if (iphlen >= sizeof(*iph))\" wrapper around\nthe fixup branch becomes redundant; left in place to keep the\npatch minimal and backport-friendly.  A follow-up can unwrap it.\n\nNote that commit 86f4c90a1c5c (\"ipv4, ipv6: ensure raw socket\nmessage is big enough to hold an IP header\") ensures the message\nbuffer is large enough to hold an iphdr, but does not constrain\nthe self-reported iph->ihl.\n\nReachability: the malformed packet source is any caller with\nCAP_NET_RAW, including an unprivileged process in a user+net\nnamespace on a kernel with CONFIG_USER_NS=y.  The reproduced AH\ncrash also requires a matching xfrm AH policy on the outgoing\nroute; a container granted CAP_NET_ADMIN can install that state\nand policy in its netns.  Loopback bypasses xfrm_output, so the\ntrigger uses a real netdev.\n\nReproduced on UML + KASAN: kernel-mode fault at addr 0x0 with\nmemcpy_orig at the crash site.  Same shape reproduces inside a\nrootless Docker container with --cap-add NET_ADMIN on a stock\ndistro kernel.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-125","CWE-20"],"references":["https://git.kernel.org/stable/c/1065b9efa4126df559b03a849c139ecfae92cd25","https://git.kernel.org/stable/c/145e9afa5b905229b4788bb72c3255f5a5f77508","https://git.kernel.org/stable/c/3c5411fa4944ed99af3d9d1de750ea8169b6dac9","https://git.kernel.org/stable/c/5a564f737ec54d63e8ee221d3ff396d07586d464","https://git.kernel.org/stable/c/7725cd3b471740fd23d25ed1da722c671fb2a5d3"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-21T03:43:09.190223697+00:00"},"epss":{"cve":"CVE-2026-64114","score":0.00136,"percentile":0.03012,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}